PhD project offered by the IMPRS-gBGC in July 2021


Understanding the formation and stability of soil mineral-organic associations derived from microbial necromass in comparison to plant litter

Marion Schrumpf , Robert Mikutta , Klaus Kaiser

Background and goals

Microbial decomposition of soil organic matter (OM) is an important natural source of atmospheric CO2 concentrations and understanding the drivers of OM persistence is pivotal for climate change prediction and mitigation. The role of microorganisms for soil carbon cycling is however dual, since they not only decompose OM but also contribute to it via necromass formation after cell death. Similar to compounds originating from decomposing plant debris, microbial necromass can become stabilised by association with minerals, thus contributing to the formation of persistent soil OM. While it is assumed that microbial necromass can even dominate mineral-associated OM (MOM), little is known about the formation pathways, formation efficiency, and the microbial utilization of necromass-derived MOM. Therefore, we aim at elucidating the mechanisms behind the formation of necromass-derived MOM and its consequences for microbial access to energy and substrates.

Your tasks will involve:

  • Incubation of microbial necromass and plant litter in the presence of pristine minerals and soil samples to study their association with mineral surfaces using stable isotopes (13C) to distinguish between substrate- and soil-derived carbon
  • Analyses of evolving CO2, oxygen consumption, enzyme activities, microbial biomass and carbon use efficiencies, biomarkers, and the formation, composition and nominal oxidation state of mineral-associated carbon (NOSC).
  • Testing the stability of the formed MOM by desorption and incubation experiments, which will be related to the composition and NOSC of mineral-associated substrates.

Your profile

We are looking for a highly motivated and team-oriented PhD student interested in a scientific career. The successful candidate should have a broad interest in the drivers of soil carbon storage and turnover, and how those are linked to microbial composition, activity, and mineralogy. The project requires a strong background in soil biogeochemical processes, which should be proven by respective courses and a master in geoecology, biogeosciences, environmental sciences, forestry, physical geography, biology, or related fields of science. Finally, very good oral and written communication skills in English are required.

Working environment

The Max Planck Institute for Biogeochemistry in Jena offers an exceptional dynamic, creative, international, and multidisciplinary working environment. The successful applicant will join the Soil Biogeochemistry group, which is encompassing experimental and theoretical work on the persistence and sensitivity of organic carbon in soils, and interactions between biogeochemical cycles of carbon, nutrients, and water at all spatial scales. The project will be conducted in close collaboration with (1) Robert Mikutta and Klaus Kaiser from Martin-Luther-University Halle-Wittenberg and a second PhD student located there, and (2) Oliver Lechtenfeld from UFZ Halle for NOSC determination using ESI-FT-ICR-MS as part of the new DFG priority program “Systems Ecology of Soils – Energy Discharge Modulated by Microbiome and Boundary Conditions (SoilSystems)” (

Living in Jena

The city of Jena is not only famous for its high-tech industry, internationally renowned research institutions and a modern university, but also for its beautiful natural setting in the Saale valley with its steep limestone slopes. The climate is mild, and a large variety of plants grow in the close surroundings, including wine grapes and wild orchids. The city of Jena has a large active student scene supporting a diverse cultural life.

The Max Planck Society seeks to increase the number of women in those areas where they are underrepresented and therefore explicitly encourages women to apply. The Max Planck Society is committed to increasing the number of individuals with disabilities in its workforce and therefore encourages applications from such qualified individuals.

For further information, please contact Marion Schrumpf (

Liang et al. (2019), Global Change Biology <b>25</b>, 3578-3590 <br> Red frame depicts the stabilization of microbial necromass by minerals (entombing), but underlying mechanisms and controls are unresolved
Liang et al. (2019), Global Change Biology 25, 3578-3590
Red frame depicts the stabilization of microbial necromass by minerals (entombing), but underlying mechanisms and controls are unresolved

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